Method and apparatus for transmitting control signaling

ABSTRACT

A method and apparatus for transmitting control signaling includes: transmitting indication information on a transmission location of control signaling by a base station to a mobile station configured as an open-loop MIMO transmission mode; transmitting the control signaling by the base station in a data region by using the open-loop MIMO transmission mode or a transmit diversity transmission mode if the location for transmitting the control signaling indicated by the information on a transmission location of control signaling is located at the data region. Whereby the number of mobile stations to be scheduled in a cell is increased and results in the scheduling information to be transmitted in a subframe increased, the control signaling of a mobile station configured as an open-loop MIMO transmission mode is placed in a data region for transmission, thereby increasing the number of UE scheduled, increasing the throughput of the system.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of U.S. patentapplication Ser. No. 14/159,019, filed Jan. 20, 2014, now pending, whichis a continuation of International Application No. PCT/CN2011/077649,filed on Jul. 27, 2011, now pending, the contents of which are hereinwholly incorporated by reference.

TECHNICAL FIELD

The present invention relates to the field of communications, and inparticular to a method and apparatus for transmitting control signaling.

BACKGROUND

In a long-term evolution (LTE) system, a physical downlink controlchannel (PDCCH) is used to transmit control information, includingdownlink scheduling information (DL-grant), uplink schedulinginformation (UL-grant), and control information, etc. Signalingtransmitted in the PDCCH is referred to as downlink control information(DCI). A base station multiplexes PDCCHs of all mobile stations in acell in former several OFDM symbols of a subframe for transmission, andlatter OFDM symbols of the subframe are used for transmission PDSCHs ofthe mobile stations; wherein, a region transmitting the PDCCHs isreferred to as a control region, and a region transmitting the PDSCHs isreferred to as a data region. Currently, at most 3 OFDM symbols may beused for transmission of PDCCHs, and a typical subframe structure isshown in FIG. 1.

However, in some scenarios, there would be a case where capacity of thePDCCH is limited, that is, the capacity of 3 OFDM symbols cannot meetthe scheduling requirement of current mobile stations. In such a case,for example, in LTE Release 11, there exist multiple radio remoteheaders (RRHs) in a cell at the same time, so as to provide betterservices to mobile stations in the area. Typical deployment of a cellcontaining RRHs is shown in FIG. 2. As the transmission power of an RRHis relatively low and the RRHs are spaced apart by a relatively largedistance, mobile stations within the coverage of different RRHs mayshare the same resources; that is, comparatively speaking, in resourcesof a subframe, the number of mobile stations that may be scheduled in acell may be greatly increased. Therefore, the number of pieces ofscheduling information needs to be transmitted in a subframe will becorrespondingly increased, and conventional 3 OFDM symbols may beinsufficient for placement of scheduling information of all the mobilestations. If such a problem cannot be solved, scheduling of UE (userequipment) will be reduced, thereby lowering the throughput of thesystem.

It should be noted that the above description of the background art ismerely provided for clear and complete explanation of the presentinvention and for easy understanding by those skilled in the art. And itshould not be understood that the above technical solution is known tothose skilled in the art as it is described in the background art of thepresent invention.

SUMMARY

A method and apparatus for transmitting control signaling are providedin the embodiments of the present invention, so as to solve the problemthat the capacity of the PDCCH is limited by placing the controlsignaling of a mobile station configured as an open-loop MIMOtransmission mode in a data region for transmission.

According to one aspect of the embodiments of the present invention,there is provided a method for transmitting control signaling, and themethod includes:

transmitting indication information on a transmission location ofcontrol signaling by a base station to a mobile station configured as anopen-loop MIMO transmission mode; and

transmitting the control signaling by the base station in a data regionby using an open-loop MIMO transmission mode or a transmit diversitytransmission mode if the location for transmitting the control signalingindicated by the indication information on a transmission location ofcontrol signaling is located at the data region.

According to another aspect of the embodiments of the present invention,there is provided a base station, including:

a first transmitting unit configured to transmit indication informationon a transmission location of control signaling to a mobile stationconfigured as an open-loop MIMO transmission mode; and

a second transmitting unit configured to transmit the control signalingin a data region by using an open-loop MIMO transmission mode or atransmit diversity transmission mode if the location for transmittingthe control signaling indicated by the indication information on atransmission location of control signaling is located at the dataregion.

According to still another aspect of the embodiments of the presentinvention, there is provided a computer-readable program, wherein whenthe program is executed in a base station, the program enables acomputer to carry out the method for transmitting control signaling asdescribed above in the base station.

According to still another aspect of the embodiments of the presentinvention, there is provided a storage medium in which acomputer-readable program is stored, wherein the computer-readableprogram enables a computer to carry out the method for transmittingcontrol signaling as described above in a base station.

The advantage of the embodiments of the present invention resides inthat in a case where the number of mobile stations that need to bescheduled in a cell is increased and it is resulted in that thescheduling information needing to be transmitted in a subframe isincreased, the control signaling of a mobile station configured as anopen-loop MIMO transmission mode is placed in a data region fortransmission according to the method and apparatus of the embodiments ofthe present invention, thereby increasing the number of UE the can bescheduled, increasing the throughput of the system, and solving theproblem that the capacity of the PDCCH is limited.

With reference to the following description and drawings, the particularembodiments of the present invention are disclosed in detail, and theprinciple of the present invention and the manners of use are indicated.It should be understood that the scope of the embodiments of the presentinvention is not limited thereto. The embodiments of the presentinvention contain many alternations, modifications and equivalentswithin the spirits and scope of the terms of the appended claims.

Features that are described and/or illustrated with respect to oneembodiment may be used in the same way or in a similar way in one ormore other embodiments and/or in combination with or instead of thefeatures of the other embodiments.

It should be emphasized that the term “includes/including” when used inthis specification is taken to specify the presence of stated features,integers, steps or components but does not preclude the presence oraddition of one or more other features, integers, steps, components orgroups thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

Many aspects of the invention can be better understood with reference tothe following drawings. The components in the drawings are notnecessarily to scale, emphasis instead being placed upon clearlyillustrating the principles of the present invention. To facilitateillustrating and describing some parts of the invention, correspondingportions of the drawings may be exaggerated or reduced in size, e.g.,made larger in relation to other parts than in an exemplary deviceactually made according to the invention. Elements and features depictedin one drawing or embodiment of the invention may be combined withelements and features depicted in one or more additional drawings orembodiments. Moreover, in the drawings, like reference numeralsdesignate corresponding parts throughout the several views and may beused to designate like or similar parts in more than one embodiment. Inthe drawings:

FIG. 1 is a schematic diagram of the typical structure of a subframe;

FIG. 2 is a schematic diagram of the network structure of a cellcontaining RRHs;

FIG. 3 is a flowchart of the method for transmitting control signalingprovided by Embodiment 1 of the present invention;

FIG. 4 is a processing flowchart of transmitting control signaling in adata region in a TxD manner;

FIG. 5 is a processing flowchart of a transmission end in a closedloop/open loop MIMO transmission mode in an existing standard;

FIG. 6 is a processing flowchart of a transmission end in which openloop MIMO adopts a rank of 1 in a future LTE system;

FIG. 7 is a flowchart of precoding processing in an open loop MIMOtransmission mode in an existing standard;

FIG. 8 is a processing flowchart of a transmission end transmittingcontrol signaling in a data region in an open loop MIMO transmissionmode in an embodiment of the present invention; and

FIG. 9 is a schematic diagram of the structure of the base stationprovided by Embodiment 2 of the present invention.

DETAILED DESCRIPTION

Foregoing and other features of the embodiments of the present inventionwill become apparent with reference to the drawings and the followingdescription. These embodiments are illustrative only and are notintended to limit the present invention. For easy understanding of theprinciple and embodiments of the present invention by those skilled inthe art, the embodiments of the present invention shall be describedtaking a method for transmitting control signaling in an LTE/LTE-Asystem as an example. However, it should be appreciated that theembodiments of the present invention are not limited to said system, andare applicable to any system relating to transmission of controlsignaling.

An embodiment of the present invention provides a method fortransmitting control signaling, as described in Embodiment 1 below.

Embodiment 1

FIG. 3 is a flowchart of the method for transmitting control signalingprovided by Embodiment 1 of the present invention. Referring to FIG. 3,the method includes:

step 301: transmitting indication information on a transmission locationof control signaling by a base station to a mobile station configured asan open-loop MIMO transmission mode;

wherein, the indication information on a transmission location ofcontrol signaling is used to indicate a transmission location of thecontrol signaling, the transmission location here being in a controlregion, i.e. a conventional PDCCH region, or being in a data region,i.e. a conventional PDSCH region;

step 302: transmitting the control signaling by the base station in adata region by using an open-loop MIMO (Multiple Input Multiple Output)mode or a transmit diversity (TxD) mode if the location for transmittingthe control signaling indicated by the indication information on atransmission location of control signaling is located at the dataregion.

For a mobile station configured as an open-loop MIMO transmission mode,this embodiment provides a method for transmitting control signaling;wherein the region for transmitting control signaling is changed from aconventional PDCCH region into a data region, and the transmission modemay be an MIMO transmission mode, or may be a TxD transmission mode.

If the control signaling is transmitted in the data region in the TxDtransmission mode, the procedure of transmission of the controlsignaling is the same as that in the TxD transmission mode in anexisting standard. Taking that 2 antennas are used at a transmission endas an example, a procedure of processing is as shown in FIG. 4. Thetransmission end uses only a link of modulation and coding, that is,there exists correspondingly one codeword only. Source bit information,such as the control signaling in this embodiment, is channel encoded andsymbol modulated, and the generated symbols are layer mapped, with thelayer number of the layer mapped being referred to as a rank, which is 2in FIG. 4; and the layer mapped data are precoded, and the generatedsymbol sequence is mapped onto allocated resource elements, and isfinally transmitted via antennas, wherein, input symbol of the precodingis vector

$\begin{bmatrix}x_{1} \\x_{2}\end{bmatrix},$

and output symbol of the precoding is matrix

$\begin{bmatrix}x_{1} & x_{2}^{*} \\x_{2} & {- x_{1}^{*}}\end{bmatrix}.$

If the control signaling is transmitted in the data region in an openloop MIMO transmission mode, the modulation and coding scheme of thecontrol signaling is the same as that in the open loop MIMO transmissionmode in an existing standard, but the layer mapping and precoding schemeof the control signaling are different from the layer mapping andprecoding scheme in an existing standard. For clarity and easyunderstanding of the method for transmitting control signaling in thedata region in the open loop MIMO transmission mode of this embodiment,transmission of data in a data region in an open loop MIMO transmissionmode in an existing standard and transmission of control signaling in adata region in an open loop MIMO transmission mode in an embodiment ofthe present invention shall be described in detail in a comparativemanner.

FIG. 5 is a processing flowchart of transmission of data in a dataregion in a closed loop/open loop MIMO transmission mode in an existingstandard. Referring to FIG. 5, there are mainly two types oftransmission modes of a base station configured as an MIMO transmissionmode, one is open loop MIMO transmission mode, and the other is closedloop MIMO transmission mode, wherein, the open loop MIMO transmissionmode is mainly configured for a mobile station of a relatively highmoving speed, a precoding matrix adopted by a base station needs not tobe fed back by a mobile station, and the precoding matrix is designatedby the base station following a certain rule; and the closed loop MIMOtransmission mode is configured for a mobile station of a relatively lowmoving speed, and a precoding matrix adopted by a base station isobtained according to a precoding matrix index fed back by a mobilestation and a predefined codebook.

In an existing standard, transmission end models in an open loop MIMOtransmission mode and a closed loop MIMO transmission mode areanalogous. Taking a transmission mode in which two antennas are used andthe rank is 2 as an example, a procedure of transmission of thetransmission end is as shown in FIG. 2. It can be seen from comparisonof FIGS. 4 and 5 that a difference between the open/closed loop MIMOtransmission mode and the TxD transmission mode resides in that the linknumbers of modulation and coding of the transmission ends are differentwhen they are configured with a rank of greater than or equal to 2. Forthe TxD transmission mode, the link number of the modulation and codingof the transmission end is 1, and for the open/closed loop MIMOtransmission mode, the link number of the modulation and coding of thetransmission end is 2 when the rank is greater than or equal to 2.

In an existing standard, if a mobile station configured as an open loopMIMO transmission mode really adopts the open loop MIMO transmissionmode, the minimum rank is 2, and the minimum rank that may be adopted inthe closed loop MIMO transmission mode is 1. And for a mobile station inan open loop MIMO transmission mode, if the requirement of a currentchannel cannot be met when the rank is 2, it may return back to the TxDtransmission mode. Furthermore, in a future LTE system, the loop MIMOtransmission mode may possibly support a mode in which the rank is 1,and in this case a model of the transmission end is shown in FIG. 6.

In an existing standard, the transmission end in the open loop MIMOtransmission mode may be expressed as y=w×D×U×x, that is, the precodingmatrix includes three parts: matrix W, matrix D and matrix U. Takingthat two antennas are used and the rank is 2 as an example, a processthat transmission signals pass through the matrix D and the matrix U isshown in FIG. 7. It can be seen that before passing through the matrixW, each symbol in each layer includes signals from codeword 1 andcodeword 2, that is, an effect of diversity is achieved. If there existsno such an effect of diversity, that is, the transmission signals passthrough the matrix W directly but not pass through matrices D and U, anadverse effect will be brought to the decoding of a codeword mapped ontoa layer when a channel state in this layer suddenly deteriorates. In anexisting standard, a precoding matrix in the closed loop MIMOtransmission mode includes only one matrix W′.

FIG. 8 is a processing flowchart of transmitting control signaling in adata region in an open loop MIMO transmission mode in an embodiment ofthe present invention. Referring to FIG. 8, this embodiment is describedtaking that the rank is 2 and four antennas are used as an example.

In an embodiment, when a base station transmits control signaling in adata region in an open loop MIMO transmission mode, the rank used by thebase station in transmitting the control signaling may be the minimumrank in the supportable open loop MIMO transmission mode. That is, ifthe supportable open loop MIMO transmission mode is an open loop MIMOtransmission mode in an existing standard, the rank in transmitting thecontrol signaling in this embodiment is 2; and if the supportable openloop MIMO transmission mode is a newly-defined open loop MIMOtransmission mode and the new mode supports that the rank is 1, the rankin transmitting the control signaling in this embodiment is 1.

In another embodiment, when a base station transmits control signalingin a data region in an open loop MIMO transmission mode, the rank usedby the base station in transmitting the control signaling may also bethe rank configure by the base station for the transmission of data.That is, a value of the rank used by the control signaling in thisembodiment may be equal to that of the rank configured by the basestation for the data. For example, if the rank configured by the basestation for the data is 2, the rank used by the control signaling inthis embodiment is 2; if the rank configured by the base station for thedata is 3, the rank used by the control signaling in this embodiment is3; and if the rank configured by the base station for the data is 4, therank used by the control signaling in this embodiment is 4, and so on.

In this embodiment, when the rank used by the base station intransmitting the control signaling in the data region is greater than orequal to 2, different from an existing standard (i.e. as shown in FIG.5), the base station adopts one modulation and coding link to transmitthe control signaling. Referring to FIG. 8, first, channel coding isperformed to the control signaling; then the symbols that are channelencoded are modulated; thereafter, layer mapping is performed to themodulated symbols according to the rank; and finally, the data that arelayer mapped are precoded by using a unitary precoding matrix.

As shown in FIG. 8, in this embodiment, a unitary precoding matrix W isonly used in the processing of precoding, excluding matrices D and U.This is because that one codeword is only used and correspondingmodulation signals are allocated onto two layers, and an effect ofdiversity is achieved.

In this embodiment, if the mobile station is configured as an open loopMIMO transmission mode and the demodulation of data by it is configuredas performing channel estimation based on a specific reference signal,the control signaling transmitted together with data in the samesubframe in the data region is also performed channel estimation basedon a specific reference signal, and then is demodulated.

In this embodiment, as the data are transmitted in an open loop MIMOtransmission mode, as described above, on the basis of channelrequirements, the open loop MIMO transmission mode of the data mayreturn back to the TxD transmission mode. Hence, according to the methodof this embodiment, when it is found that the open loop MIMOtransmission mode of the data returns back to the TxD transmission mode,the transmission mode of the control signaling also returns back to theTxD transmission mode. Further more, when the base station transmits thecontrol signaling in the data region in an open loop MIMO transmissionmode, whether the base station returns back to transmitting data in aTxD transmission mode may be judged in this embodiment, and if the basestation returns back to transmitting data in a TxD transmission mode,the base station also returns back to transmitting the control signalingin a TxD transmission mode.

With the method of this embodiment, in a case where the number of mobilestations that need to be scheduled in a cell is increased and it isresulted in that the scheduling information needing to be transmitted ina subframe is increased, the control signaling of a mobile stationconfigured as an open-loop MIMO transmission mode is placed in a dataregion for transmission, thereby increasing the number of UE the can bescheduled, increasing the throughput of the system, and solving theproblem that the capacity of the PDCCH is limited.

An embodiment of the present invention further provides a base station,as described in Embodiment 2 below. As the principle of the base stationfor solving problems is similar to that of the method for transmittingcontrol signaling based on a base station in the above-describedEmbodiment 1, the implementation of the method may be referred to forthe implementation of the base station, and the repeated parts shall notbe described any further.

Embodiment 2

FIG. 9 is a schematic diagram of the structure of a base stationprovided by an embodiment of the present invention. As shown in FIG. 9,the base station includes:

a first transmitting unit 91 configured to transmit indicationinformation on a transmission location of control signaling to a mobilestation configured as an open-loop MIMO transmission mode; and

a second transmitting unit 92 configured to transmit the controlsignaling in a data region by using an open-loop MIMO transmission modeor a transmit diversity transmission mode if the location fortransmitting the control signaling indicated by the indicationinformation on a transmission location of control signaling is locatedat the data region.

It can be seen from Embodiment 1 that the base station of thisembodiment provides a method for transmitting control signaling for amobile station configured as an open loop MIMO transmission mode,wherein the region for transmitting control signaling is changed from aconventional PDCCH region into a data region, and the transmission modemay be an open loop MIMO transmission mode, or may be a TxD transmissionmode. Hence, the problem that the capacity of the PDCCH is limited for amobile station configured as an open loop MIMO transmission mode issolved.

In an embodiment, when the second transmitting unit 92 transmits thecontrol signaling in the data region by using an open-loop MIMOtransmission mode, the rank adopted by the second transmitting unit 92in transmission of the control signaling is the minimum rank of thesupportable open-loop MIMO transmission mode.

In another embodiment, when the second transmitting unit 92 transmitsthe control signaling in the data region by using an open-loop MIMOtransmission mode, the rank adopted by the second transmitting unit 92in transmission of the control signaling is the rank configured by thebase station in transmission of data;

wherein, if the rank adopted by the second transmitting unit 92 intransmission of the control signaling is greater than or equal to 2, thesecond transmitting unit 92 transmits the control signaling via onemodulation encoding link; and wherein, the second transmitting unit 92includes:

a channel encoding module 921 configured to perform channel encoding onthe control signaling;

a modulating module 922 configured to perform modulation on channelencoded symbols;

a layer mapping module 923 configured to perform layer mapping on themodulated symbols according to the rank; and

a precoding module 924 configured to precode the layer mapped data byusing a unitary precoding matrix.

In this embodiment, the control signaling transmitted by the secondtransmitting unit 92 in the data region uses a dedicated referencesignal to perform channel estimation, so as to facilitate demodulation.

In this embodiment, when the base station transmits the controlsignaling in the data region by using an open-loop MIMO transmissionmode, the base station further includes:

a judging unit 93 configured to judge whether the base station returnsto transmitting data by using a transmit diversity transmission mode;

and the second transmitting unit 92 returns back to transmitting thecontrol signaling by using a transmit diversity transmission mode if theresult of judgment of the judging unit 93 is positive.

With the base station of this embodiment, in a case where the number ofmobile stations that need to be scheduled in a cell is increased and itis resulted in that the scheduling information needing to be transmittedin a subframe is increased, the base station places the controlsignaling of a mobile station configured as an open-loop MIMOtransmission mode in a data region for transmission, thereby increasingthe number of UE the can be scheduled, increasing the throughput of thesystem, and solving the problem that the capacity of the PDCCH islimited.

An embodiment of the present invention further provides acomputer-readable program, wherein when the program is executed in abase station, the program enables a computer to carry out the method fortransmitting control signaling as described in Embodiment 1 in the basestation.

An embodiment of the present invention further provides a storage mediumin which a computer-readable program is stored, wherein thecomputer-readable program enables a computer to carry out the method fortransmitting control signaling as described in Embodiment 1 in a basestation.

The above apparatuses and methods of the present invention may beimplemented by hardware, or by hardware in combination with software.The present invention relates to such a computer-readable program thatwhen the program is executed by a logic device, the logic device isenabled to carry out the apparatus or components as described above, orto carry out the methods or steps as described above. The presentinvention also relates to a storage medium for storing the aboveprogram, such as a hard disk, a floppy disk, a CD, a DVD, and a flashmemory, etc.

The present invention is described above with reference to particularembodiments. However, it should be understood by those skilled in theart that such a description is illustrative only, and not intended tolimit the protection scope of the present invention. Various variantsand modifications may be made by those skilled in the art according tothe spirits and principle of the present invention, and such variantsand modifications fall within the scope of the present invention.

What is claimed is:
 1. A method for receiving control signaling in amobile station in open-loop MIMO transmission mode, the methodcomprising: detecting control signaling which is transmitted by a basestation based on the dedicated reference signal, where a rank adopted bythe base station in transmission of the control signaling is a minimumrank of a supportable open-loop MIMO transmission mode.
 2. The methodaccording to claim 1, wherein the control signaling is transmitted bythe base station in a data region by using a preconfigured open-loopMIMO transmission mode or a transmit diversity transmission mode if thelocation for transmitting the control signaling indicated by indicationinformation on a transmission location of control signaling transmittedby the base station is located at the data region.
 3. The methodaccording to claim 2, the detecting assumes transmit diversitytransmission mode, if indicated by the base station to detect PDSCHtransmitted by the base station using transmit diversity transmissionmode.
 4. A mobile station in open-loop MIMO transmission mode,comprising: a receiver to detect a control signaling which istransmitted by a base station based on the dedicated reference signal,where a rank adopted by the base station in transmission of the controlsignaling is a minimum rank of a supportable open-loop MIMO transmissionmode.
 5. The mobile station according to claim 4, wherein the controlsignaling is transmitted by the base station in a data region by using apreconfigured open-loop MIMO transmission mode or a transmit diversitytransmission mode if the location for transmitting the control signalingindicated by indication information on a transmission location ofcontrol signaling transmitted by the base station is located at the dataregion.
 6. The method according to claim 5, the receiver assumestransmit diversity transmission mode, if indicated by the base stationto detect PDSCH transmitted by the base station using transmit diversitytransmission mode.